Patent GB-962887-A (GB)
Title: Rotary impact tool
IPC: B25B21/02
Filed: 1963-02-25
Abstract: 962,887. Screwing-up and unscrewing bolts. SKIL CORPORATION. Feb. 25, 1963 [Sept. 11, 1962; Sept. 28, 1962], No. 7423/63. Heading B3N. A rotary impact tool 20 for tightening bolts comprises a rotary air motor 24 drivingly connected to a hammer 52 having equally-spaced reciprocable impact jaw members 61 adapted to be normally urged by springs 66 so that their ends are out of the line of engagement with radial arms 78 formed on an anvil 54, cam means 82 being provided in the hammer for contact with the rear ends 64 of the jaws in order to project the jaws forwardly into position for delivering impact blows to the anvil arms in predetermined sequence with the rotation of the hammer. The air motor 24 is provided with a shaft 26 coupled by splines 58 to the body of the hammer 52 in which the jaws 61 are housed in pockets 52 at its forward end. The anvil 54 is formed with a shank 74 on which the cam means 82 is slidably mounted, the cam being keyed for rotation with the hammer. An intermediate cam plate 84 is freely mounted on the shank between the cam 82 and a third cam 86, the latter cam having a limited rotational movement determined by the co-operation of a recess 96 in the cam and a pin 97 fixed in the shank. In operation, before air is fed to the motor via inlet 34, valve 39, passage 40, valve 42, passage 49 and reversing valve 32, the jaws are retracted out of the line of engagement with the arms 78 of the anvil. Upon engaging a wrench, adapted to be attached to the end 72 of the anvil, with the head of a bolt and depressing the valve 42, the hammer is rotated and, by means of the interengagement of cam lobes 90, 92, 94 and 98 formed on the three cam plates 82, 84 and 86, the extensions 88 on the cam plate 82 depress the jaws into such a position that they strike the arms 78 of the anvil. Simultaneously with or immediately after the striking action, the cam lobes are in such a position as to permit the jaws to move out of the line of engagement with the arms under the action of the springs 66, thereby allowing the air motor to accelerate in readiness for the next impact. The shaping of the cam lobes is such that the hammer may be rotated in the reverse direction. In the modification shown in Fig. 15, the three cam plates are replaced by two cams 160 rotatably mounted on pins 161 secured in the hammer 140. The cams are provided with teeth 162, Fig. 18, engaging with teeth 157 formed on the end of the shank 154 of the anvil 142. In the normal inoperative position of the tool, ends 151 of the jaws are urged by springs 150 into contact with lands 164 on the cams. Upon actuation of the tool as previously described, the hammer rotates thereby, due to the mating of the teeth 162 and 157, causing lobes 165 on the cams to depress the jaws outwardly so that they strike the arms 159 of the anvil. The lobes are symmetrically shaped so that the tool may be operated in the reverse direction. The ratio of the number of teeth in the cams to that in the shank is preferably arranged so that the hammer rotates twice before the jaws are actuated to strike the anvil. Instead of teeth, a chain or friction drive may be used.